What does coelomate mean?
A coelomate is any animal whose body contains a true coelom: a fluid-filled internal cavity completely lined with tissue derived from the mesoderm, one of the three embryonic germ layers. This structure separates the gut from the outer body wall and allows internal organs to grow, move, and be cushioned independently of the body surface. In biological classification, the presence or absence of a coelom is fundamental: animals are grouped into acoelomates (no cavity), pseudocoelomates (a cavity only partly lined with mesoderm), and coelomates (a fully lined cavity). Familiar coelomates include annelid worms, molluscs, arthropods, echinoderms, and all vertebrates, including humans. The word functions chiefly as a noun but also appears adjectivally, as in 'the coelomate body plan'. It belongs firmly to scientific register, appearing almost exclusively in zoology and evolutionary biology contexts.
nounAn animal that possesses a coelom, the fluid-filled body cavity lined with mesoderm that lies between the digestive tract and the body wall. The term is also used adjectivally in zoology to describe such animals or body plans.
- A zoological term for an animal whose body contains a true coelom — a fluid-filled cavity completely lined with mesoderm tissue.
- Used adjectivally to describe anything relating to or characteristic of such animals (e.g. 'the coelomate condition').
"Earthworms are true coelomates, with organs suspended in a well-developed body cavity."
"Annelids and molluscs are classic examples of coelomate phyla."
"The presence of a mesoderm-lined cavity marks these organisms as coelomates rather than pseudocoelomates."
Standard plural; used when referring to multiple animals or taxa possessing a coelom.
"Most familiar animals, from insects to mammals, are coelomates."
Your body cavity has a lining so important that whether an animal has it defines entire branches of the animal kingdom.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coelomate
Coelomate derives from the Greek koilōma, meaning 'hollow' or 'cavity', itself from koilos, 'hollow'. The term entered English scientific usage in the nineteenth century as biologists formalized the classification of animal body plans. It shares its Greek root with coelom, the name of the cavity itself, and with related terms such as acoelomate and pseudocoelomate.
Related word forms
How coelomate is actually used
Strictly technical vocabulary used mainly in zoology, comparative anatomy, and evolutionary biology textbooks; rare in everyday speech.
Easily confused with coelomate
Coelom is the body cavity itself; a coelomate is an animal possessing that cavity.